Effect of drilling process on hole quality, delamination of CFC
Tutor / directorGhassemieh, Elaheh
CovenanteeQueen's University of Belfast
Document typeMaster thesis (pre-Bologna period)
Rights accessOpen Access
Defects during the drilling process in carbon fibre laminates can result in late stage rejections in the aerospace industry. This project shows a comprehensive analysis of the influence of drilling parameters on hole quality and delamination. Also, optimum drilling conditions are presented. Drilling at different parameters with both drills uncoated and coated allowed the examination of the impact of the drilling parameters and the drill’s coating on the results. Although during the machining unexpected high temperatures damaged the top surface of the work-piece, measurements of peel-up delamination at the holes entrances showed that it was improved by using a high feed rate and a low spindle speed. Push-out delamination could not be measured due to the poor quality of the holes exits. The overheating and the poor hole quality at the exits of the holes were mainly caused by the drill’s geometry, which was proved to not be the most adequate for the job. Drilling parameters also influenced both problems, which were increased when a low feed rate and a high spindle speed were used. In these same conditions the drills suffered the most wear and damage too. Although the drill’s coating showed no impact on delamination or hole quality results, it was an effective solution regarding tool wear. A second study regarding drilling conditions was carried out to improve the overheating and the poor holes quality achieved at the exits in the first study. The results showed that the use of coolant avoided high working temperatures and the use of a sacrifice board led to clean exits in where the delamination factor could be calculated.